This invention relates to a method of inspecting a hard-to-access surface area of a component.
There are many available techniques for inspecting metal surfaces such as optical microscopes and profilers having styluses. These methods work well for inspecting rolled steel or large surface areas where microscopes, cameras, and styluses are accessible. However, these techniques do not work well when inspecting the metal on internal surfaces or other hard-to-access areas such as gear teeth. Direct optical surface finish measurement of fine pitch gears is difficult because of line-of-sight problems. The adjacent tooth prevents the surface positioning perpendicular to the light beam. Angular positioning leads up to 20% loss of the reflected light. Replicas became necessary for fine pitch gears to get surface finish inspection without gear destruction. Further, these methods frequently require that a portion of the surface to be inspected be cut from the main article of manufacture and is thus destructive. A non-destructive method is therefore necessary to monitor accumulative damage.
Accordingly, an epoxy-based replicating technique was developed. The technique involves applying a petroleum distillate, which contains 10 to 12 chain-linked hydrocarbons, to the surface to be inspected. Finely ground charcoal must be mixed with the epoxy to provide proper reflective quantities. The mixture is then applied to the surface. After the mixture hardens, the replicated surface is removed and inspected. This technique has certain drawbacks. The ratio of ingredients must be precise or the replicated surface will not have proper reflective qualities. Further, if the mixture is not completed in 30 seconds, the replicating properties are sharply reduced. Accordingly, a new replicating technique is needed.
Accordingly, it is an object of this invention to provide an improved method of inspecting a surface in inaccessible areas without damaging the original article of manufacture and that does not depend on precise ratios of ingredients.
The present invention overcomes a compromised encountering of prior art by providing a method for inspecting the surface finish of a component by first providing an original surface. A release agent is then applied to the original surface. An epoxy mixture is then applied onto the original surface over the release agent. After the epoxy mixture hardens into a replicated surface, it is removed. A metallic coating is then applied to the replicated surface and the replicated surface is then inspected.
In another embodiment of the invention, the epoxy mixture comprises charcoal.
In yet another embodiment of the invention, the step of applying metallic coating comprises sputtering a metallic coating of gold, aluminum, or silver.